Other than the fact there are neither telephones, telephone poles, telephone
wires, nor phone reception of any kind, Telephone Canyon is well-named. I
understand there was once some sort of government project, during World War I,
apparently, to string telephone wire through the canyon. Exactly what the
purpose of that might have been is hard to fathom, but, considering its
difficulty, surely it must have
been a major part of the effort to win the war in Europe. Sadly, though, no
telephone system was ever installed in the canyon, and to this day you can't
phone home from there except by satellite. Nevertheless, the name "Telephone
Canyon" was coined and has stuck. And, amazingly, in spite of the failure of
this critical project, the war was won anyway.

We camped in the uppermost regions of the canyon. Suitable camping sites are
pretty hard to find - no surprise there for such a remote area. So we were
elated to find a bare spot large enough to pitch a tent. Such a spot is easy
to lose in the expanse of the desert, so my brother formulated a brilliant
answer to the question of how to relocate it after our hike down the canyon.
His sotol-ution to this problem is pictured in the introductory image above.
(For more on sotol, click:
sotol.)

This is what you see as you descend through the upper reaches of Telephone
Canyon - extremely rugged terrain resulting from the erosion of the resistant
limestone of the lower
Cretaceous Santa Elena
Formation. At this point you are at around 4000 feet near the summit of a
tilted fault block as explained in
Telephone Canyon I. You are
following the erosional pattern created by the Heath Creek drainage
system.

The Heath Creek drainage system has cut from west to east through the
northwest-southeast-trending
fault-block
mountain ranges, forming Telephone Canyon. This implies the drainage
preceded the tectonic activity that created these mountains. As the mountains
rose, the easterly flowing creek just continued to cut down into the rock as it
was lifted up. As you make your way down the canyon, you can see the
stratigraphic
relationships in this area. The following photograph shows the resistant Santa
Elena Limestone forming ridges at the top of the slopes. Debris from the ridges
covers lower parts of the Santa Elena and the Sue Peaks Formation, which lies
below the Santa Elena. The Sue Peaks Formation is more easily eroded and tends
to form slopes rather than ridges.

In the following image, my brother trudges down the Heath Creek drainage
with a typical Telephone Canyon scene in the background. You can see the
cave-like erosional patterns in the Santa Elena. Below that, the Santa Elena
Limestone and the Sue Peaks Formation are covered by erosional rock debris
called talus. Looking back at
the image above, you can see the
angle of repose,
which is the steepest angle at which loose material can be piled. When more
talus is added to the slope by rock falls, the slope eventually is
over-steepened and the material slides to re-establish this angle. A typical
angle of repose on talus slopes is about the same as the one in the photo
above, around 30°. (In physics we call this re-establishment process
"self-organized criticality". And, for you physics weenies out there, a slope
of 30° corresponds to an effective static coefficient of friction of about
0.6. For you non-physics weenies this means a talus block, on average, will
slide if the downslope force on the block due to its weight is 60% of the
force pressing the block to the slope.)

You follow a tributary of Heath Creek down the canyon. About two-thirds of
the way to the Strawhouse Trail head, you come upon the confluence of this
tributary with Heath Creek, which flows from the north out of a dramatic valley
formed by another one of these nearly vertical, north-south-trending
faults that are
responsible for the
fault-block-mountain terrain you are hiking through. The first image below is of the west side
of this valley as seen from the canyon, looking northward. The second image is
of the east side.

The west side is uplifted with respect to the east side. In the picture
below you can see the identification of the Santa Elena Limestone, the Sue Peaks
Formation, and the Del Carmen Limestone. The Sue Peaks is a unit of relatively
easily eroded limey sediment, whereas the Del Carmen is resistant, forming
ridges like the Santa Elena. The topography continues to rise in elevation to
the northwest on the west side of the valley, with the highest points being the
twin Sue Peaks, 5845 and 5854 feet, about four miles away.

I was puzzled concerning the east side of Heath Creek Canyon. The
geologic map published by Ross A. Maxwell and included in his book, The Big
Bend of the Rio Grande shows the east side of the canyon to be all Santa
Elena, whereas in the picture below I thought I was able to confidently identify
both the Sue Peaks Formation and the Del Carmen Limestone on the east side of
the canyon. From the topographic maps, it appeared the cliffs are about 600
feet lower on the east compared to the west, implying something like a 600-foot
vertical offset along the fault. However, if Maxwell was correct, and the rocks
on the east side are all Santa Elena, this would mean something more like a
1200-foot vertical offset.

The new geologic map of Big Bend by the USGS (Scientific
Investigations Map 3142) continues to show the east side of Heath Creek
Canyon to be all Santa Elena. I was motivated to take a close look at the
satellite images on Google, and after examining those images, I'm satisfied
that the east side of Heath Creek Canyon is indeed Santa Elena. Looking further
north up the canyon, it appears that the slope in the picture above is not
typical, as there is more cliff topography on the east side of the valley
farther to the north, which would be consistent with the more resistant nature
of the Santa Elena Formation. Additionally, the offset between the rocks on the
west and east side of the canyon discussed above depends on the cliffs
referred to being correlated. That is, the rocks they are composed of must
have been continuous before
separated by erosion. That assumption appears to be in error.

Below, brother Randy is consulting his GPS as we approach the juncture with
the Strawhouse Trail and the Sierra del Caballo Muerto (Dead Horse Mountains).
The creek bed consists of limestone debris. At first, I
thought the yellow outcrops in the distance were the yellowish
marl of the Sue Peaks
formation, following the map of Ross Maxwell. However, the stratigraphic
relationships didn't seem to work out. After returning from the park and
looking over the pictures, it seemed to work better to
consider the yellow outcrops to be the Telephone Canyon Formation, which is of
a similar lithology to Sue Peaks and the cliffs above to be the Del Carmen
Limestone.

This is a closeup of what was indicated to be an outcrop of Sue Peaks
Formation on Maxwell's map. Note the cavities, indicating erosion of a unit
containing lime. I began to wonder if this
might really be the Telephone Canyon Formation. If this were true, the outcrop
above it would be the Del Carmen Limestone and that below the Glen Rose
Formation. The problem for me with the idea that this was the Sue Peaks
Formation had to do with my supposition of the presence of the Sue Peaks on
the east side of Heath Creek Canyon, coupled with the fact that the sedimentary
beds in this area generally dip westward. Therefore as you walk eastward
in Telephone Canyon you should see older and older rocks. If the Sue Peaks is
exposed on the slopes to the west, you should see older rocks exposed farther
east, where these photos were taken. If the yellow outcrops were Sue Peaks,
you would think there would have to be some structure, such as folding or
faulting, to account for these younger rocks being exposed here. Yet, we saw no
evidence of such structure, nor is there any on Maxwell's map, which is all I
had at the time.

However, if the east side of Heath Creek Canyon is indeed all
Santa Elena, as it certainly appears to be on satellite imagery, then there is
no problem with identifying the yellow outcrops pictured above as
belonging to the Sue Peaks formation. Well, except for this. As far as I know,
the latest and greatest mapping that focused on
this area was by A. R. Moustafa, whose
work was published in Geologic Quadrangle Map No. 54: Structural
Geology of Sierra del Carmen, Trans-Pecos Texas, Bureau of Economic
Geology, UT Austin, 1988. This map shows the Sue Peaks Formation outcropping on
the north side of Telephone Canyon east of Heath Creek Canyon with the Del
Carmen Limestone appearing across the canyon floor on the south beneath the Sue
Peaks. The new map and Maxwell show Santa Elena on both sides of the canyon as
you proceed east from Heath Creek Canyon, changing to the Sue Peaks Formation
on both sides as you continue east. The Sue Peaks shows up first on the north
side of Telephone Canyon, then on the south side farther along. No Del Carmen
Limestone appears in these maps in this area of the canyon.
The outcrop in the picture above therefore seems to support Moustafa,
with the Del Carmen present below the Sue Peaks. Otherwise, the
differences between the maps are minor. Sorting this all out, the
yellowish rocks appear to be the lower marly shale member of the Sue Peaks
Formation with the gray limestone member above. In addition, Moustafa
wrote that the lower member was topped by a
limestone ledge. That appears to be the case in the picture as well, although
the "ledge" in the picture may be just the lower bed, as the ledge is supposed
to be much thicker than what is shown. Alternatively, it could be that the
ledge is not as thick here as elsewhere. So, check
out my revised (from an earlier incarnation of this field trip) interpretation
of this outcrop in the images below.

On to another paradox. The next photo is that of my brother, Randy,
at the Strawhouse Trail head. The geological puzzle here is the origin of
the red rock at the top of the cairn. There are no red-rock outcrops in the
entire canyon, so the origin of this one rock is a mystery ;-).

Wildlife was not abundant, to say the least. For one thing the day was
very windy with gusts reaching close to 40 mph. Nevertheless, we did come
across a small covey of quail.

We also met a couple of fellows who had hiked with knapsacks from the
Telephone Canyon Trail head and aimed to make it all the way down the
Strawhouse Trail that evening. It was already mid-afternoon by the time they
turned south down that trail, and they still had twelve miles to go as the crow
flies. We hope they made it. At least there was a full moon. If you are young
and strong, you might be able to cover ground at three mph on a trail of low to
moderate difficulty, which meant it took them at least four more hours to make
it to Boquillas. Six or seven would be more realistic, considering they would
be hiking in the dark much of the time. Realizing how short daylight was this
time of year, we decided to forego hiking farther down the canyon through the
Sierra del Caballo Muerto and turned back. This was disappointing, but we
needed to get settled before dark.

On the trail back to camp, you get a dramatic view of the southern-most
mountain on the west side of Heath Creek Valley. Below is a telephoto. Note
the stratigraphic sequence from Santa Elena on top, to Sue Peaks, to a
prominent ridge of Del Carmen toward the bottom.

We got back to camp in time to cook some dinner in the waning light and
break out the rum and tequila; for, after all, this was New Year's Eve. And
what an evening it was with a full blue moon (using the "second full moon of
the month" definition of a blue moon) and magnificent isolation. It was also
damned cold, but we raised our spirits by raising our spirits, sitting on a
downed Spanish dagger that served as a nice couch. Quite a New Year's
to remember.